Joffrey was originally betrothed to Sansa Stark, whom he kept captive in King's Landing after he beheaded her father for treason, as Eddard Stark tried to reveal the truth about his parentage. However, he later set Sansa aside in favor of Margaery Tyrell, as part of the new alliance between House Lannister, the primary supporters of Joffrey, and House Tyrell, the ruling house of the Reach whose support helped save King's Landing from Stannis Baratheon's attack.

Contents

Biography

Background

Joffrey is believed to be the oldest son and heir of King Robert Baratheon and Queen Cersei Lannister, both of whom entered into a political marriage alliance after Robert took the throne by force from the Mad King Aerys II Targaryen. In reality, his father is Jaime Lannister, the queen's brother and the Lord Commander of the Kingsguard. He has a younger sister, Myrcella, and a younger brother, Tommen , both whom are also the product of Jaime and Cersei's incest.[2]

Joffrey takes after his mother in terms of looks and personality, his blonde hair being a subtle clue that he isn't really a Baratheon, who famously always possess black hair even when one of their parents possesses blonde hair. He is usually accompanied by his sworn shield, the formidable Sandor Clegane, who is better known as the Hound. Even before he ascends to the Iron Throne, Joffrey is spoiled, arrogant, cowardly, and sadistic; however these traits are further exacerbated upon Robert's death and his ascension to the crown.[3]

Joffrey is charming and polite towards Sansa.[4] However, he shows no sympathy when Bran falls from a tower and is severely injured, and has to be physically chastised by his uncle Tyrion before he will pay his respects to Bran's parents.[5]
While on the Kingsroad to King's Landing, Joffrey is walking with Sansa and chances upon her sister Arya practicing sword play with a commoner, Mycah. Joffrey sees a chance to have some fun with Mycah, who is too scared to move. Joffrey accuses him of assault on a noble girl and makes a cut on his face with his sword, but Arya hits Joffrey, allowing the butcher's boy to get away. When Joffrey turns on Arya, her direwolf Nymeria overpowers Joffrey, injuring him, and Arya throws his sword in the river. Joffrey begs for his life. Sansa offers aid, but Joffrey is angry at her because she saw him weak and defeated. Later, he lies about the incident and says he was attacked in an unprovoked manner. King Robert knows Joffrey is lying, and is disgusted that Joffrey let a little girl disarm him, but agrees to forget about the incident in return for the death of Nymeria.

When she cannot be found, Sansa's direwolf Lady is executed instead.[5]

In King's Landing, Joffrey tells his mother about how he would handle the people of the North as she treats his injury. He suggests capturing Winterfell, taxing the people hard and forcing their warriors to join a "royal army". Cersei elucidates the flaws in his plan and warns Joffrey that a king needs to be more careful in choosing his battles. Cersei tells her son that, "Everyone who isn't us is an enemy". She also urges Joffrey to do something nice for Sansa to win back her goodwill.[6]

Eddard Stark discovers that Joffrey isn't King Robert's son and rightful heir, by examining the family history and realizing that black hair is a dominant trait in the Baratheon line. Eddard realizes that Joffrey's true parentage can be attributed to the incestuous relationship between his mother and his "uncle" Jaime Lannister. Meanwhile, Joffrey wins back Sansa's affection by giving her a pendant.[7]

When King Robert Baratheon is grievously wounded in a hunting injury, he talks to Joffrey on his death bed and says he could have been a better father. Joffrey ascends the Iron Throne. He orders that preparations be made to crown him within the fortnight. Eddard refuses to recognize Joffrey's claim to the Iron Throne. He

presents a proclamation from Robert making him Regent and Protector of the Realm to enforce his authority, but Cersei tears up the document. Eddard expects Lord Petyr Baelish and Commander Janos Slynt of the City Watch to take Cersei and Joffrey prisoner, but is betrayed. Eddard is taken into custody and his remaining guards and household are murdered.[8]

Sansa is taken captive as well, but Arya manages to escape into the city. Joffrey dismisses Ser Barristan Selmy from the Kingsguard and names his "uncle" Jaime as the new Lord Commander. Barristan is shocked, as the Kingsguard are sworn to serve for life, and it is legally impossible to dismiss one of their members. Joffrey listens to Sansa's pleas for her father, and he agrees to show mercy to Lord Eddard if he admits treason and recants his claim that Joffrey has no right to the throne. Sansa is sure that he will.[9]

Joffrey is present at the Great Sept of Baelor for Eddard's public trial where, due to threats to Sansa's life, he confesses to treason and acknowledges Joffrey as the true king. Joffrey, playing to the crowd, reveals that his mother and his betrothed have both urged him to spare Eddard's life and exile him to the Wall (this deal had been worked out involving Queen Cersei, Varys, Grand Maester Pycelle, the High Septon, and Yoren waiting in the crowd to take him in custody). Joffrey had been told to spare him, but surprises everyone by saying that his mother and betrothed have the weak hearts and constitutions of women, while he has no mercy for traitors. He orders Ser Ilyn Payne to bring him Eddard's head. Payne carries out the order, while Sansa faints from shock and Cersei - aware this will fuel the war with the Starks - angrily tries

and fails to overrule her son.[10]
Days later, Joffrey holds court. Marillion sings a song he wrote about King Robert and Queen Cersei, which includes lyrics saying that the boar may have disemboweled Robert, but the "lion in his bed" (the Lannister's sigil is a lion) was the one who tore his balls off. Joffrey is displeased by the song and its insults against his parents. He forces the minstrel to choose between having his hands or tongue removed, then orders Ser Ilyn to instantly carry out the order, ripping out his tongue in front of the entire horrified court. Joffrey and his guards escort Sansa out of the courtroom and he states to her that she will be kept captive there and will still marry him; he also casually mentions that his mother said he should "put a son in you" as soon as Sansa has had her blood. They arrive at the castle's wall, where there are several heads mounted on long spikes - one is revealed to be Ned's. When Sansa is appalled, Joffrey angrily points to another spike carrying the head of Septa Mordane, revealing that he also needlessly killed Sansa's own Septa. She confronts him about his promise to show

mercy to her father, but he says it was mercy, as he gave him a quick death. Then Joffrey forces her to look at the severed heads, and he says that he will give her Robb's head on a spike as well if he were to be defeated by the Lannisters, prompting her to reply: "Or maybe he'll give me yours."

Joffrey is infuriated, but restrains himself from striking her as he says "Mother tells me a king should never strike his lady" - so he simply calls on Ser Meryn Trant to strike her for him, and the knight slaps Sansa hard across the face twice. Sansa comes up behind Joffrey on the walkway, obviously thinking of pushing him, though it would mean her death. The Hound realizes this and stops her, under the pretense of wiping the blood off her lip.[11]

Robb Stark continues to win victories against Joffrey's Lannister allies. Furious, Joffrey has Sansa Stark brought into the throne room. Before the whole court, he demands she answer for her brother's treason and threatens to kill her with a crossbow. Instead he orders Meryn Trant to strip and beat her. Tyrion interrupts the proceedings and scolds Joffrey for his behavior, as Sansa is his future queen. When Joffrey retorts that as king he can do whatever he wishes, his uncle reminds him that the mad king thought he could do whatever he wanted as well, and ended up being overthrown.

Joffrey torments Ros and Daisy

Talking to Bronn, Tyrion decides that Joffrey is at an age when sexual frustration might be an issue, and this could be one reason for his torment of Sansa. He then sends Joffrey two prostitutes, Ros and Daisy, as a belated nameday present. Joffrey forces one prostitute to brutally beat the other as a message to Tyrion that he will tolerate no further interference.[15]

Joffrey at the riot.

Joffrey attends the departure of his sister Myrcella Baratheon for Dorne as part of a marriage alliance pact. Joffrey is confronted by an angry populace as he makes his way back to the Red Keep. One onlooker throws some cow dung at him and Joffrey triggers a city wide riot by ordering his heavily outnumbered guards to kill everyone in the crowd. He barely escapes the riot under the protection of his Kingsguard and Tyrion publicly berates him for being a "vicious idiot". When they realize Sansa has been lost in the chaos, Joffrey callously commands that she be left to the mob; Tyrion has to point out that if any harm comes to Sansa then his uncle Jaime, a prisoner of the Starks, will be killed in retaliation.[16]

Joffrey and Tyrion on the walls of King's Landing.

King Stannis Baratheon sails on King's Landing with a fleet of over 200 ships. Joffrey is determined to fight personally, scaring his mother. Cersei suspects that Tyrion is encouraging Joffrey and plots to blackmail him into ensuring Joffrey's safety by imprisoning his lover. Joffrey tours the sea wall of the city with Tyrion and insists that he will kill Stannis himself. His bravado is undercut by his woeful lack of appreciation of the danger he is in; he stupidly suggests that they should be planning to assault Robb rather than defending their capital.[17]

Joffrey procures a new sword for the Battle of the Blackwater, naming it "Hearteater." He forces Sansa to meet him in the Throne Room before going to the city walls, making her kiss the blade and claiming that when he returns it will have Stannis' blood on it. Sansa carefully undermines his claim by questioning if he will fight in the vanguard. Joffrey is frustrated by not being made aware of Tyrion Lannister's plans to defend the city and angrily threatens his uncle. The absence of the Royal Fleet frightens Joffrey. He is pleased when Tyrion's wildfire explosion decimates Stannis' fleet. However, his courage wanes when he sees the size of the landing force that comes ashore. A sortie led by the Hound fails to drive the attackers back. The Hound then deserts his place on the Kingsguard rather than go back out. Joffrey is relieved when Ser Lancel Lannister tells him that the Queen has ordered him back to the Red Keep and ignores Tyrion imploring him to stay and lead. His cowardly exit damages the morale of the men but Tyrion is able to rally them into a further sortie, protecting the gates from a battering ram. Tyrion is wounded during the fighting but the battle is won by the arrival of a host of House Lannister and House Tyrell soldiers under the command of Lord Tywin Lannister.[18]

Joffrey rewards Tywin by naming him Savior of the City. He also grants a favor to House Tyrell for their aid and Ser Loras asks Joffrey to unite their houses in marriage. Joffrey balks at setting aside his betrothal to Sansa, but is easily convinced in a sham dialogue with his mother and courtiers and agrees to marry Margaery Tyrell.[19]

King Joffrey is passing through Flea Bottom in a heavily guarded palanquin. The Riot of King's Landing recently occurred in this part of the city. His convoy suddenly stops moving because his betrothed Margaery Tyrell insists on interacting with the smallfolk and visiting an orphanage. Later that night, he has dinner with Margaery, her brother Loras, and his mother Cersei. Cersei tells Margaery that the king barely survived the recent riot, but Joffrey explains that they were not in any real danger. He also defends Margaery's actions, to Cersei's discomfort.[20]

While fitting clothes in his chambers, Cersei asks Joffrey what he thinks about Margaery, and he says the alliance with the Tyrells will help them defeat the northern rebellion. Cersei asks what he thinks about her personally, but Joffrey dismisses her questions. Later, Joffrey summons Margaery to his chambers. Joffrey is holding his new crossbow and asks why she was married to traitor Renly Baratheon and why she failed to give him a child. Margaery tells Joffrey that she doesn't believe Renly was interested in women. Joffrey says he is considering making homosexuality punishable by death. He then demonstrates to Margaery how to use a crossbow.[21]

will be held. Joffrey tells Margaery about the history of the dead Targaryen kings. Margaery feigns interest, then they hear a crowd of smallfolk outside. Margaery suggest they greet them, and Joffrey is reluctant but has the doors opened. Joffrey and Margaery step outside to a happy, cheering crowd, while Cersei looks on angrily.[22]

Ros is caught spying on Lord Petyr Baelish, so Lord Baelish gives her to Joffrey, who brutally kills her in his chambers with his crossbow.[23]

Joffrey summons his HandTywin Lannister to the throne room. Joffrey asks for a report of the small council meetings, and Tywin invites him to attend the small council meetings. Joffrey complains that Tywin holds the meetings in the Tower of the Hand, which requires him to climb many stairs. Joffrey squirms as Tywin approaches the throne, and Tywin tells him that he can be carried to the tower. Joffrey then asks for information on the rumors about Daenerys Targaryen and her dragons. Tywin confirms the rumors are true, and Joffrey demands to know what is being done about it. Tywin tells him it is not his concern, and he should leave such matters to his advisers.[24]

At the wedding of Tyrion Lannister and Sansa Stark, Joffrey escorts Sansa to the altar. He then removes Tyrion's stool, so he cannot reach Sansa's shoulders to cloak her. Joffrey laughs when Tyrion is unable to

cloak her. When Sansa excuses herself from her table during the feast, Joffrey follows her, and suggests he might pay a visit to her chambers that night after Tyrion passes out. Joffrey then calls for the bedding ceremony, and Tyrion insists there will be no bedding ceremony. Tyrion threatens the king, which infuriates Joffrey. Tywin says they can do without the bedding ceremony, and Tyrion says he was only joking, feigning being drunk so as not to anger Joffrey to the point where he might order harm upon him.[25]

At a meeting of the small council, Joffrey gleefully informs Tyrion of the deaths of Robb Stark and Catelyn Stark. He tells Grand Maester Pycelle to thank Walder Frey for his service and wants to serve Robb's head to Sansa at his wedding feast. Lord Varys and Tyrion take offense to this, and Tyrion threatens the king again. Tywin interjects by saying that he has won Joffrey's war for him. Joffrey angrily states that his supposed father won the real war, while Tywin hid in Casterly Rock during the fighting. Tywin orders that Joffrey be put to bed, and given Essence of Nightshade to sedate him. Joffrey is taken to his chambers by Cersei.[26]

to Jaime Lannister that the people of King's Landing know that he "saved the city" in the Battle of Blackwater and they know that he "won" the War of the Five Kings, and is convinced that there will not be a riot at the wedding.[27]

At a breakfast celebration on his wedding day, Joffrey receives various gifts. Among them, he is given a book by his uncle Tyrion, and a Valyrian steel sword forged from Ned Stark's sword Ice by his grandfather Tywin. Pleased with the gift, he promptly destroys the book with his new sword, to the horror of his guests. He says the sword needs a name; one guest suggests Widow's Wail, which gets Joffrey's approval.

In the Sept of Baelor at the purple wedding celebration, Joffrey and Margaery are wed. At the wedding feast, a band plays The Rains of Castamere; Joffrey throws money them and tells them to go away. Later, Dontos Hollard performs in front of the royal family and Joffrey promises a gold dragon to whoever knocks Dontos' hat off which leads to many objects hurling at his head. Joffrey then announces some entertainment that he has organized: a group of dwarfs crudely re-enacting the War of the Five Kings and fighting each other. Joffrey laughs hysterically during the show, spitting wine all over himself, though many others in attendance clearly find the spectacle distasteful.

Joffrey during his wedding feast.

Once the dwarf show is over, Joffery turns his attention to Tyrion and suggests he borrow a costume and join in. Tyrion politely declines and suggests that the King himself take part, with a veiled reference to Joffrey's cowardice at the Battle of the Blackwater. Joffrey responds by pouring his wine over Tyrion's head and appointing Tyrion his new cupbearer. As the crowd watch in stunned silence, Joffrey drops his goblet and orders Tyrion to pick it up, then kicks it away and tells Tyrion to pick it up again. Joffrey demands that Tyrion kneel before him. Tyrion silently refuses. The stand off is interrupted by the arrival of the big wedding pie, which is cut by Joffrey with Widow's Wail, and doves come flying out of it.

Joffrey lies dead in his mother's arms after drinking wine poisoned with the strangler.

While Joffrey is eating his pie, he commands Tyrion to stay to bring him his wine. Tyrion does this and asks to leave, which Joffrey refuses. After drinking his wine, Joffrey starts choking violently. As he gasps for air he staggers down from the high table and starts vomiting on the floor. Jaime runs from the crowd, and Cersei from the high table. Cersei holds her son in her lap. His face has turned purple, and blood is running from his eyes and nose. With a last gesture, Joffrey looks up at Tyrion, who has picked up the goblet to examine it for poison, lifts an accusing finger in his direction, and then dies of asphyxiation. Cersei immediately accuses Tyrion of poisoning her son and demands that he be arrested.[28]

Joffrey's body is displayed at the Great Sept of Baelor.

​Joffrey's funeral is held at the Great Sept of Baelor, which Cersei, Tommen and Tywin attend to pay their respects. Tywin informs Tommen that with Joffrey's death, the crown will pass to him. Over Joffrey's corpse, Tywin lectures Tommen on what it takes to be a good king, despite Cersei's feeble complaints that this is neither the time nor the place for this. He opines that Joffrey was neither a wise nor a good king, and that had he been, he may still be alive. After Tywin leaves and Jaime arrives, Cersei is adamant that it was Tyrion who killed Joffrey, and asks Jaime to kill him to avenge their son. Jaime scornfully asks why he was forced to love such a hateful woman, and they angrily have sex in front of their son's corpse.[29]

After Joffrey's death his younger brother Tommen succeeds him as king. Other than his mother Cersei, Joffrey was not particularly mourned by anyone. Even his own alleged supporters had come to see him as a hindrance to future Lannister political goals. Tywin openly scorned him in front of his own corpse when it was laid in state, and said he was a bad king.[30]

Though gone, Joffrey's death has devastating consequences. Tyrion is put on a farcical show-trial for Joffrey's murder and he demands a trial by combat, a decision that ultimately leads to the near-fatal injury of Gregor Clegane and the deaths of Prince Oberyn Martell, Shae and Tywin himself. For his part, Tyrion is freed by Jaime from imprisonment and smuggled out of Westeros after he is sentenced to death. Olenna Tyrell later confides to Margaery that it was she who poisoned Joffrey in order to protect her from Joffrey's beastly nature that he had very clearly displayed with Sansa, and Petyr Baelish reveals to Sansa that he and Dontos Hollard provided Olenna with the poison.

At no point did Joffrey control all of the Seven Kingdoms. In the first year of his reign his faction only controlled the Westerlands, the Crownlands, and a narrow strip of the southern Riverlands between the two. By the second year of his reign his faction managed to gain control of most of southern Westeros: after the Battle of the Blackwater, he had gained control of the Stormlands and the support of the Reach, with the Vale and Dorne at least neutral to his reign. For the few short weeks between the death of Robb Stark and Joffrey's own death, he nominally extended his control over the North (under the Boltons) and Riverlands (under the Freys), though functional control would take some time, as scattered Stark-Tully holdouts continued to resist. Stannis remained free and in defiance of Joffrey on Dragonstone, while Joffrey never controlled the Iron Islands at all (with the continued attacks of the ironborn remaining an ongoing problem into his younger brother's reign).[31] The constant civil wars of Joffrey's time on the Iron Throne drained the remaining financial resources of the crown and House Lannister, drastically exacerbating what was already a massive debt crisis with the Iron Bank of Braavos.[32]

Personality

Joffrey was cruel, arrogant, sadistic, and a tyrannical ruler. However, he was also incompetent, unintelligent, naive, petulant, cowardly, and prone to rash outbursts of violence. Much like earlier Targaryen kings, it was suspected that Joffrey's psychopathic behavior was a result of his incestuous bloodline. Joffrey was consumed by megalomaniacal delusions of grandeur. Even though he was absurdly unskilled at ruling, making far more problems than he solved, he was convinced that he deserved praise and utter devotion from everyone around him. Despite the fact that at the start of the War of the Five Kings most of the realm rose in rebellion against him, to the point that his faction essentially controlled only the Westerlands, the Crownlands, and a narrow strip of the southern Riverlands between them, Joffrey was convinced that he was the greatest king in the history of the Seven Kingdoms. Added to what was an unstable personality to begin with, Cersei utterly spoiled and indulged Joffrey his entire life, resulting in him possessing a massive sense of entitlement which knew no rational bounds. Moreover, his father-figure King Robert was largely absent from his life and a terrible role-model, with his constant drinking and whoring (though Robert, at least, lamented on his deathbed that he hadn't been a good father).

Joffrey was deceitful, but showed even less tact than his mother. He was willing to take advantage of the trust that Sansa Stark initially placed in him, when she was blinded by fantasies of marrying her handsome prince. In general, however, Joffrey was usually too short-sighted to bother lying, often simply committing various atrocities in public, without concern for the consequences.

Joffrey was obsessed with the self-conception that he was a great warrior like King Robert, but displayed no martial skill. Joffrey never raised a weapon against an enemy combatant in his entire life. Particularly, despite the fact that his faction was losing the war and bracing for a siege in King's Landing, Joffrey insisted that was the time for him to strike against the Stark forces as they were distracted by the Fall of Winterfell. However, Tyrion pointed out that his own city was on the verge of attack by Stannis's superior forces.

Aptly described as a vicious idiot by his uncle Tyrion, Joffrey was not simply a ruthless tyrant, but absurdly incompetent. While Robert was also not skilled at ruling (though not as bad as Joffrey), he was at least respected as a great warrior. Joffrey, in contrast, had no redeeming values whatsoever: literally his only claim to rule was that he was the son of Robert, the previous king. The great irony, of course, was that Joffrey was actually Jaime's bastard son and had no valid claim to the throne, but a shockingly large number of Joffrey's followers continued to blindly obey his crazed orders without question.

Once in a while, Joffrey does make a valid point, such as that the feudal levy system in the Seven Kingdoms is somewhat antiquated, or that his advisors should be worried that Daenerys Targaryen reportedly hatched three new dragons in Essos, or that his grandfather Tywin Lannister bided his time before he finally aided the rebels during Robert's Rebellion. Generally, however, Joffrey only rarely made a valid insight as a means for the narrative to underscore that everyone else is overlooking something, i.e. "if someone as stupid as Joffrey realized this, it should have been obvious to everyone else". Even on those first two points Joffrey was quite short-sighted: he was concerned about Daenerys in the far east, despite the fact that Robb Stark was already leading major armies in rebellion in Westeros itself, and didn't consider that he should concentrate on the much more immediate threat (which is how Tyrion reacted to news of Daenerys). Similarly, while he vaguely said that having a standing royal army was better than using feudal levies, Cersei had to explain to him that his suggestion for how to make one was too impractical to work (if a royal army conscripts men from the North, they still wouldn't feel enthusiastic about attacking their fellow Northmen). Joffrey may also have been correct when he said that the Stark forces were distracted after the Fall of Winterfell, and that would have been the perfect opportunity to strike, but once again Tyrion had to remind him that his own city was preparing for a siege by Stannis Baratheon.

Despite all these negative traits, however, Joffrey is shown to be capable of feeling emotion. On Robert's deathbed, he is visibly shocked and sad at the thought that his (legal) father may be dying and holds his hand, and (in the books) it is stated by various characters that Joffrey was very fond of Sandor Clegane despite his outwardly aloof manner towards him.

Behind the scenes

Gleeson's naturally dark hair needed touching up every single day he shot to keep it Lannister blonde. His hair was also kept short because it makes him look younger.[34]

Gleeson was born in Cork, Republic of Ireland. He is a student of Trinity College Dublin and a member of DU Players. As a result, Gleeson's natural speaking voice actually has a pronounced Irish Cork accent: the upper-class, Received Pronunciation accent he adopts while playing Joffrey on-screen is a conscious part of his performance. In the Blu-ray commentary for "Lord Snow", Sophie Turner (Sansa Stark) explains that for amusement between takes, the English-accented Turner and Irish-accented Gleeson would imitate one another's accents.

Gleeson said his performance was influenced by numerous Hollywood villains, in particular Joaquin Phoenix's performance as the crazed, petulant Emperor Commodus in the movie Gladiator.[35]

In the books

In the A Song of Ice and Fire novels, Joffrey is twelve years old when the story begins. He is described as a handsome young man, with the gold hair and green eyes of the Lannisters, and is tall and strong for his age. His uncle Tyrion occasionally tries to teach him something of politics and learning, but he is uninterested in such matters, more interested in warring. He and Robert have a distant relationship, but his mother dotes upon him. Throughout the books, Cersei is willfully blind to Joffrey's insane and homicidal behavior, no matter how ridiculous. Rather than recognize the monster that she has unleashed on the Seven Kingdoms by putting Joffrey on the throne, Cersei embraces the fantasy that he is a great king, or at worst "willful", and chides her younger son Tommen that he should try to be more like Joffrey. Later books also retroactively reveal that Tommen has lived in terror of Joffrey his entire life. Joffrey killed and skinned several of Tommen's childhood pets, yet Cersei continued to dote on him. At one point Tommen even says that he used to "go away inside" mentally when Joffrey did certain things to him, though the exact extent of what he did (killing his pets or something far more sinister) has not been made clear. At one point, Joffrey, as a child, was told that a kitchen cat was pregnant. Upon this discovery, he cut open the cat and took out the unborn kitten fetuses. He presented the fetuses to his "father", wanting to gain approval from him, but Robert was shocked and disgusted by this action, which caused him to hit Joffrey so hard that two of his baby teeth are knocked out, and is thought to be dead. Cersei brushes off Joffrey's actions as some nonsense with a cat, and threatens to kill Robert in his sleep. Many of Joffrey's cruel actions are his attempt of being more like his "father"

The reason for Joffrey's sociopathic, borderline-insane behavior is suspected to be due to his incestuous parentage, much like some of the earlier Targaryen kings. However, Joffrey also had a distant relationship with his "father" Robert, his mother spoiled him, and he lacked any good role models throughout his childhood, which heavily contributed to his mental instability. From a strict technical standpoint, Joffrey is not "insane" in the sense that King Aerys II Targaryen was, in that he didn't suffer from hallucinations. Otherwise, Joffrey is a megalomanical sociopath by any measure.

In the second book, A Clash of Kings, Joffrey at several points shoots and kills peasants with his crossbow, for largely imagined insults. When crowds of refugees from the war he started come to the castle gates to beg for bread, he picks them off with his crossbow from the battlements, for daring to consider him "a baker". He then brags about doing this in open court, before having Sansa stripped and beaten in front of everyone. When Sansa asks if he killed any of the peasants, Joffrey matter-of-factly states that of course he did, he was trying to kill them. He also expresses fondness for making men fight to the death and giving "justice" to criminals.

Bastardy

Fans sometimes derisively assume that "Joffrey Baratheon" should really be called "Joffrey Lannister", because of his status as the bastard offspring of the incestuous relationship between Cersei Lannister and Jaime Lannister, and not the son of King Robert Baratheon at all. This is actually in error, as according to the customs of bastardy, Joffrey doesn't even have the right to use the surname "Lannister". As Jaime's bastard son, given birth to by a woman from the Westerlands (Cersei), Joffrey would have to use the bastard surname for the Westerlands: "Joffrey Hill". There's also the possibility that he might be called "Joffrey Waters" given that both Jaime and Cersei had been living in the Crownlands for many years, and Joffrey lived his whole life there. All of this, of course, would only happen if Jaime were to openly acknowledge Joffrey as his son, which is an impossibility given the disastrous political fallout this would create. Further, as the product of not merely bastardy, but incest, the Faith of the Seven would want to outright kill Joffrey as an abomination before the gods if his actual parentage were ever revealed. Therefore from a strict legal standpoint, given that Jaime will never acknowledge his children with Cersei, Joffrey has no right to any surname, and should properly just be called "Joffrey" as if he were a lowborn commorer. However, since a husband is the legal father of his wife's children (the reason why a wife's infidelity is illegal), Joffrey is a Baratheon.

Age

Joffrey is stated to be 17 years old in the TV series at the time of the Battle of the Blackwater, as stated in "The Prince of Winterfell". Most of the younger characters in the TV series were aged-up by about two years compared to their book counterparts (i.e. Sansa states that she is 13 years old in the first episode of Season 1, but is 11 in the first novel). Making Joffrey 17 years old in the TV series drastically increases his age relative to the other characters, however, as he is stated to be only 13 years old during the Battle of the Blackwater in the novels (the Tournament he holds in the beginning of book/Season 2 is to celebrate his nameday). This would make TV-Joffrey 16 years old in Season 1, which is stated to be 17 years after Robert and Cersei were married at the end of Robert's Rebellion (which was increased from 15 years ago in the TV series). Cersei also states that she became pregnant with a son by Robert at the very beginning of her marriage who died in infancy. Assuming that Cersei's first son died even a few days after birth, this requires a nine month pregnancy, plus another nine month pregnancy before Joffrey was born (assuming she became pregnant quite soon after her first son died), meaning Joffrey could have been born no earlier than sixteen and a half years before the beginning of the narrative - drastically increasing Joffrey's age to sixteen years old in Season 1 strains the plausibility of this timetable, and drastically increasing his age by four years instead of two like the other characters may have been a dialogue error in "The Prince of Winterfell", in order to make a forced comparison between Joffrey and how Jaime was such a skilled warrior at seventeen that he became the youngest man ever to join the Kingsguard.